For the standards for Peripheral Component Interface Express (PCIe) version 2.7 (dated Jan. 15, 2007) and Universal Serial Bus (USB) version 3.0 (dated Nov. 17, 2008), each protocol provides seamless mechanisms to detect cable connections, which is accomplished through the use a receive or RX detect feature. However, the Serial Advanced Technology Attachment (SATA) revision 2.6 standard (which dated Mar. 7, 2007 and which is incorporated by reference for all purposes) does not specify any way to detect cable attachment or detachment for either cabled or socket applications. This deficiency poses a disadvantage for mobile applications (i.e., notebook personal computers (PCs)) that support an external-SATA (eSATA) port.
Turning to FIG. 1, an example of a conventional system 100 can be seen. System 100 generally comprises a host system 102 that communicates with an external device 104 (i.e., a hard disk drive) through a SATA compliant cable 106. To accomplish this, cable 106 is coupled to an external-SATA (eSATA) compliant connector 108, and a redriver 110 (such as the Texas Instruments Incorporated's SN75LVCP412) provides communications between connector 108 and SATA host 112 over communication link 114. With this configuration and when the external device 104 is disconnected or detached, host 112 continuously sends communication reset signals (or out-of-band signals) to initiate a response from the external device 104, which may be connected at any time. Needless to say, the nearly continuous transmission of the communication reset signals from the host can waste a considerable amount of power.
To address this solution, at least in part, the SN75LVCP412 from Texas Instruments Incorporated uses an Auto Low Power (ALP) Mode. In particular, this ALP mode is entered when there is not differential transaction or the link to the external device is in an electrical idle state. However, this redrive, like many other redrivers, only addresses power consumption by the redriver; the host may continue to use power through the transmission of communication reset signals. Therefore, there is a need for a method and/or apparatus that performs cable detection and reduces power consumption.